Building Defects Investigations - the correct procedure

Unscientific investigation and imprecise reporting is
potentially more descriptive of the level of competence of the surveyor than of
the condition of the surveyed building.

A Trading Standards
office requested the preparation of evidence for the prosecution of a
damp-proofing company.

The company under
investigation held rising damp and groundwater to be unrelated.From this, they offered a new ‘quick fix’ for
damp walls.They attracted custom by
promising to cure damp without inconvenience to occupants.Troublesome damp-proof courses could be
ignored as they played no part – an approach which was as attractive as it was
unscientific.It was not, however,
simply the technical merit of their ‘cure’ which was being investigated but the
adequacy of their surveys and advice to customers.

They operated by
carrying out free surveys.With each
survey report, they confused the potential customer with a profoundly
impenetrable description of the mechanisms of rising damp and the working of
their ‘cure’.This mystery dressed in
scientific clothing aside, their reports followed an all-too-common pattern, being
based on the ill-informed use of electrical-resistance moisture meters.

To evaluate their work, their survey of a traditional,
solid-wall, brick, terraced house, was studied.The house was typical of its age and construction.It exhibited the usual limited resistance to
damp, suffering minor intermittent problems which varied with the seasons.

Their survey report showed commendable consistency, being as
unscientific in the interpretation of the moisture meter readings as it was
casual in describing the process of investigation and obscure in explaining
cause and remedy:

no check on the meters accuracy was reported,

the calibration of the meter was not given,

no check for contaminants, such as salts, was recorded and

the degree of dampness was over-reported because the meter was calibrated for use in wood but was used to measure moisture in plaster, and the results interpreted as direct moisture content readings.

A check for salt
deposits, where moisture readings are interpreted as symptomatic of rising
damp, is fundamental.The presence of
surface salt deposits makes electrical-resistance moisture meter readings
unreliable.Conversely, the absence of
such salts reduces the likelihood of rising damp being the cause of the
moisture found.

Isolated moisture
measurements alone rarely show the cause of the dampness.Corroborative evidence is required and is
often readily obtainable by, for example, taking a moisture profile of the
suspect wall.Clarity, thoroughness and
completeness are good watchwords for reporting defects investigations.

In the presentation
of his findings, the company’s surveyor made clear his lack of understanding of
scientific technique, whilst failing in his objectives of demonstrating the
presence of rising damp and the appropriateness of the remedial works he
proposed.